The present invention relates, in general, to network modules and, more particularly, to selecting or accessing network modules connected to a common communication bus.
One type of network module widely used in applications such as automotive, building ventilation, and general industrial applications is a sensor module. Sensor modules sense a physical condition such as pressure, temperature, or acceleration and provide an analog electrical signal representative of the sensed physical condition. The sensor's analog electrical output signal is then converted to a digital electrical output signal via an analog-to-digital (A/D) converter present in the sensor module. Typically, sensor modules include a microprocessor unit (MPU) or a microcontroller unit (MCU) that has A/D conversion capability. The digital electrical output signal is then routed directly to another MPU or MCU (which serves as a master, slave, or peer) or the networked sensor module enters an idle mode until a request for information is received.
A drawback of conventional networked sensor modules is that for a number of "N" networked modules, "N" extra conductors (wires) are needed in addition to the common bus to uniquely address each module. More particularly, the cost of conductors represents a significant portion of the total system cost for systems having more than a few network modules. In addition, the number of I/O pins on an MCU/MPU limits the number of conductors that may be coupled between the MCU/MPU and the common bus.
Accordingly, it would be advantageous to have a method and a means for increasing the number of network modules coupled to a bus from 1 to "N," and that permits addressing each network module without increasing the number of conductors for addressing each module.